A power amplifier providing greater than 10 Watts of power requires a relatively high primary voltage to enable an efficient radio frequency (RF) generation. On the other hand, transistors included in a circuit, which provide a digital waveform for modulating an RF signal for transmission, require low operating voltages, such as 1 to 2 volts. These transistors are typically susceptible to a low voltage breakdown and, generally, need protection from high voltages that may be reflected from the output side of a power amplifier. Impedance mismatches between the output side of a power amplifier and its load (such as an antenna) may produce a high voltage standing wave ratio (VSWR) that forms a voltage likely to exceed the safe operating margins of the transistors generating the digital waveform.
Due to operating voltage differences, separate circuits are typically required between a circuit used for generation of signal waveforms and a circuit used for generation of RF power. Hence, the need for separate digital waveform modulators and RF power amplifiers.
Conventional circuits using complimentary metal-oxide-semiconductor (CMOS) fabrication techniques cannot synthesize a waveform directly at an antenna for transmission at high RF power levels. The present invention includes a composite device that may be used for RF power generation and low voltage CMOS interfacing.